The Time of the Doctor - S7-E17
Corrected entry: When Clara sees The Silence, her reaction is fear, but she was born after the Moon Landing and would have to have seen it at some point in her life, so her reaction should be to kill them all on sight.
Correction: "Different universe." This is the Doctor's response when asked why the Silence were no longer being killed in "The Wedding of River Song." Even if that is not the case, this is an entirely different breed of Silence we've seen previously.
MasterOfAll